1. Field of the Invention
This invention relates to film processing apparatus and, more particularly, to an improved multipurpose film handling cassette for exposing, processing and projecting images of photographic film.
2. Description of the Prior Art
Multipurpose photographic cassettes have been developed for use in motion picture photographic systems capable of processing an exposed strip of photographic material to a viewable condition as illustrated and described in such prior references as U.S. Pat. No. 3,615,127 issued to Edwin H. Land on Oct. 26, 1971; U.S. Pat. No. 3,623,417 issued Nov. 30, 1971 to Vaito K. Eloranta; and U.S. Pat. No. 3,748,994 issued July 31, 1973 to Joseph A. Stella, all of which are owned by the assignee of the present invention.
In such systems, use is made of a film handling cassette within which the several operations of exposure, chemical processing, drying and projecting of the recorded images are accomplished without transferring the film from the cassette. In this arrangement, the strip of photographic film contained in the cassette may be exposed in a camera adapted to receive the cassette and then processed to provide viewable images by placing the cassette in a viewing apparatus equipped to activate the cassette-contained processor upon rewinding the exposed film strip. After processing in this manner, the viewing apparatus is operated as a projector to advance the film incrementally frame by frame past a light source for viewing of the recorded images.
In this arrangment, the unexposed photosensitive strip, initially wound upon a supply reel, preferably passes from the supply reel through a normally inoperative processing station and then across an opening of the cassette which functions at different intervals as both an exposure and projection station. Beyond the exposure station, this film is wound onto the takeup reel.
When substantially the entire length of the photosensitive strip in the cassette has been exposed and wound onto the takeup reel, the cassette is then loaded into a special purpose projector in which the motion of the film is reversed, i.e., it passes from the takeup reel back onto the supply reel. In its movement in this reverse direction, the film strip itself actuates the normally inoperable processing station so that the film strip is subjected to processing treatment in which a thin layer of processing fluid is supplied to the portion of the film emulsion intermediate the film margins by means such as, for example, a doctor blade in communication with and supplied with processing fluid passing through a nozzle which in turn communicates with a processing fluid reservoir. Immediately following processing fluid deposition, in response to further film advancement, a valve member is actuated to move into blocking engagement with the processing fluid nozzle thus terminating further passage of processing fluid from the reservoir. Following a predetermined delay period, the film strip bearing the still wet layer of processing fluid, now wound upon the supply spool again, is then again advanced through the now inoperable processing station and through the exposure/projection station for projection and completion of drying of the film.
It will be appreciated that, following the deposition of the processing fluid layer upon the film and during the above-described advancement of the still wet film back through the processing station and the projection/exposure station for the initial projection and drying operations, it is critical that the flow of processing fluid through the nozzle be completely and positively terminated. Accordingly, it is desirable to seal off the nozzle immediately following deposition of the processing fluid upon the film strip. As briefly set forth above, in prior designs, incorporated in the processor is a slidable nozzle valve which is utilized to close off the processor nozzle and thereby disable the processor immediately following treatment of the film strip with the processing fluid. In relation to the nozzle opening, the valve is positioned initially in front of or upstream of the nozzle opening in terms of film strip travel during rewind, i.e., during deposition of processing fluid. Additionally, a pressure pad component is positioned beneath the nozzle opening in a position such that a film engaging surface on the pressure pad is directly under the nozzle opening to thereby retain and interpose incremental portions of the film strip firmly against the downwardly facing surface of the fluid applicator housing.
Following the processing operation, and responsive to engagement by a film discontinuity or the like, located near the leading or takeup end of the film strip, the valve member is displaced from its initial position so that it underlies and blocks the nozzle opening. Further, during this displacement of the valve, the pressure pad is cammed downwardly away from the film strip by side cams of the valve so as to deactivate the pressure pad and to free the film strip for unrestricted travel in either direction through the processing station for subsequent projection and rewind cycles.
Accordingly, the valve member which is adapted to slide readily from its initial position to its processor disabling position serves not only to shut off the flow of processing fluid from the processor, but also serves the important function of displacing the pressure pad, which performs a critical function in spreading the desired processing fluid layer upon the film strip, during the processing operation, into a position where it will not interfere with film strip travel once the processing has been accomplished. Accordingly, it will be appreciated that it is extremely important that the engagement between the film strip and the slide valve be achieved in each and every instance so that the slide valve may be displaced to its final position wherein it serves the above-described critical functions.
One prior art approach to displacing the slide valve from its initial position to its closed position is to provide an integrally formed spring arm extension which rides against and engages the film strip during both the exposure and processing modes of operation and which is adapted to cooperate with a triangular aperture formed in the film strip at its leading end so as to displace the slide valve into its closed position at the completion of the initial rewind, i.e., processing rewind. Such an arrangement has been found to be disadvantageous in that in order to assure positive engagement of the film strip with the spring arm of the slide valve, it was found necessary that the spring arm constantly be in contact with the surface of the film strip and, accordingly, such contact resulted in undesirable scratching of the back side of the film strip. Such an arrangement is illustrated in U.S. Pat. No. 3,772,975 entitled "Photographic Film Cassette Employing Coated Processor Valve" issued to John F. Batter, Jr. et. al. on Nov. 20, 1973.
Another prior art approach for displacing the slide valve from its initial position to its closed position makes use of a pair of notches in the opposing edges of the film strip. The slide valve is provided with a pair of spaced film strip rail engaging fingers which are spaced from one another so as to engage the film strip only at the non-image bearing edge portions. The spacing of the fingers defines a region therebetween into which the necked-down portion of the film strip defined by the edge notches is configured to pass and to positively engage the slide valve for the desired displacement in response to the driving motion of the film strip. Such an arrangement is described in U.S. Pat. No. 4,106,042 entitled "Multipurpose Film Cassette Having A Processor Disabling Valve Retention Arrangement" issued to Frank M. Czumak, et al., on Apr. 26, 1977.
Both the motion picture camera and the player with which such a cassette are used are provided with a set of fixed film side guides and a set of spring loaded or moving side guides which serve to properly guide the film strip throug the area of their respective aperture blocks. It has been found that each time the above-described notches pass through the region of the side guides, the moving side guides will be depressed into the notches as they pass thereby. Over a continued period of time, such an arrangement can cause damage to the film strip in the region of the notches and eventually could cause separation of film rails which are carried at the edges of the film strip from the base film strip itself.